1. Field of the Invention
The present invention is directed towards a new and improved dual rated live loaded packing system for a valve stem and for a valve employing such system so that at least two ranges of thrust values may be provided to exert a live load on a packing ring around the valve stem. The packing system also provides a means to determine if the preferred or prescribed thrust values are being applied.
2. Background of the Prior Art
Over the years, a wide variety of piston rod packing systems, stuffing box sealing systems, valve stem sealing and piston ring sealing systems have been developed and some of these systems have utilized a live load thrust against a packing member to facilitate sealing around the piston rod or valve stem. U.S. Pat. No. 601,614 to Dudley; U.S. Pat. No. 3,659,862 to Sebastian; U.S. Pat. No. 3,713,660 to Luthe; U.S. Pat. No. 3,968,970 to Vogeli; U.S. Pat. No. 4,582,329 to Stalph; U.S. Pat. No. 4,722,507 to Lindackers et al. and U.S. Pat. No. 5,056,757 to Wood, disclose packing or stuffing box systems in accordance with the prior art.